The present invention relates to a vehicle-loaded heartbeat meter mounted on a vehicle for measuring heartbeats of a driver or any other passengers, and more particularly to a vehicle-loaded heartbeat meter for comparing the measured result with a reference value to decide the presence or absence of abnormality and then informing the result of the decision.
When driving vehicles, the unhealthy condition of a driver leads to higher probability of accidents. For example, if the driver continues driving for a long time without rest, his health is adversely affected and concentration is reduced with accumulation of fatigue.
Heart rate is one barometer to know the condition of one's health. As a device for measuring heart rate, portable small-sized heartbeat meters have been recently commercialized. This type heartbeat meter is handy to carry anywhere, but has low measurement accuracy. By way of example, even if the driver carries such a heartbeat meter into the vehicle to know the condition of his health during driving, the vehicle must be stopped every time he desires to measure heart rate. More specifically, a typical heartbeat meter of this type comprises a light emitting diode and a photodiode both projected on a board to constitute a reflection type photosensor. In measurement, the sensor is put against the inner surface of a finger and, to avoid an adverse influence of lights coming from the exterior, the sensor and the finger are both covered with a black sponge or the like. Accordingly, the driver can not drive the vehicle with the sensor left fitted on his finger. Furthermore, that type of sensor disables the measurement if the finger is moved during measurement to shift the relative positions of the sensor and the finger, as a result of which the subject (driver) is required to keep quiet.
Meanwhile, it is preferable for a vehicle-loaded heartbeat meter to compare the measured value with a preset value, i.e., normal value and, if the compared result has proved to be abnormal, then inform the driver or any other passengers of the fact to stop driving. In conventional heartbeat meters, the normal value to be compared with the measured value was set using a variable resistor or the like. However, for setting the normal value, this method requires the troublesome operation of previously measuring heart rate in the normal condition by making use of another heartbeat meter with the measured result fixed in mind, and setting a scale on the variable resistor at the resulting value. Furthermore, because heart rate is largely different person by person, setting of the normal value must be updated every time the driver is changed from one to another to alternately drive a car.
Incidentially, UK Patent Applications GB No. 2100850, GB No. 2070240 and GB No. 2052752 are known as prior arts relevant to the present invention.